Composantes spectrales du Chaos

Nous étudions des signaux chaotiques dans le domaine fréquentiel, et non plus seulement selon les représentations de la dynamique non linéaire. L'analyse spectrale de trois récurrences non inversibles de dimension deux est réalisée, et nous nous attachons plus particulièrement aux relations entre les caractéristiques fréquentielles des signaux et les bifurcations ayant amené au chaos. Il apparaît alors que les représentations en fréquences peuvent être reliées à l'évolution dynamique du système, et fournissent des informations sur la dynamique qui ne sont pas directement disponibles autrement

MAC Protocol Operation in Energy Harvesting for 5G Networks

Two vital challenges arise in the next generation 5G networks: scarcity of spectrum and the aspect of energy efficiency (EE). In this letter, we first formulate the prime issue, i.e., energy harvesting (EV) for 5G wireless networks, in which spectrum and energy resources are efficiently received and resourcefully managed. Thereafter, we introduce a medium access control (MAC) scheme for dual tier 5G networks; it also invokes the simultaneous wireless information and power transfer (SWIPT) technique with other data transmission schemes, i.e., cooperative transmission (CT) scheme and non-cooperative transmission (NCT) scheme with EV abilities. Illustrative results demonstrate significant improvement in aggregated throughput and EE

Enhanced versions of DCSK and FM-DCSK data transmission systems

Over the past five years many different modulation schemes have been proposed for chaotic communications. Of these, the DCSK and FM-DCSK techniques offer the best noise performance. However, even the noise performance of these schemes is a few dB worse than that of the conventional noncoherent FSK technique. The paper shows how the noise performance of DCSK and FM-DCSK systems can be improved considerably. Two solutions are considered: in the first version more than one information bit is sent using the same reference signal, while in the second version the received noisy sample functions are cleaned by averaging

FM-DCSK: A novel method for chaotic communications

In binary Differential Chaos Shift Keying (DCSK), each information bit is mapped to the correlation between two pieces of a chaotic waveform. The receiver determines the correlation (which is proportional to the energy per bit) in order to demodulate the received signal. Since a chaotic signal is not periodic, the energy per bit is not constant and can only be estimated, even in the noise-free case. This estimation has a non-zero variance that limits the attainable data rate. This problem can be avoided if the energy per bit is kept constant. In this paper, the DCSK technique is combined with frequency modulation in order to achieve two properties: the excellent noise performance of DCSK is maintained; in addition, the energy per bit is kept constant in order not to limit the data rate. A low-pass equivalent model that significantly speeds up the simulation of an FM-DCSK system is also developed. Finally the noise performance of the proposed FM-DCSK system is given

Recent advances in communicating with chaos

The past few years have witnessed rapid growth in the field of mobile and indoor radio applications. Chaotic communications schemes are potentially suitable for these applications, offering simpler and cheaper solutions that currently available Spread Spectrum (SS) techniques. This paper presents an overview of the most promising chaotic communications schemes which have been developed recently and proposes some multilevel extensions of these methods to increase the data rate